Over 230 civilians killed and 120 women and girls raped by South Sudan government troops and aligned forces, UN says.

The United Nations has accused South Sudan's government forces and aligned troops of killing dozens of civilians, including children and the elderly, in deliberate and ruthless attacks this year that may amount to war crimes.

The UN human rights office (OHCHR) and the UN Mission in South Sudan (UNMISS) jointly published a report on Tuesday, documenting at least 232 civilian deaths and many more injuries between April 16 and May 24 in attacks by government-backed troops as well as armed youth on 40 villages in the opposition-held areas of Mayendit and Leer.

"The perpetrators of these revolting acts against defenceless civilians, including those bearing command responsibility, must not be allowed to get away with it," Zeid Ra'ad al-Hussein, the UN high commissioner for human rights, said in a statement, calling on the government to halt all hostilities against civilians.

In its report, the UN human rights office identified three individuals who "may bear the greatest responsibility" for the recent violations.

OHCHR said: "Civilians were targeted, with the elderly, people with disabilities and very young children killed in horrific acts of violence - some hung from trees and others burned alive in their homes."

Failed peace

Zeid called on the perpetrators of these "horrific crimes" to be held accountable and demanded justice for the victims.

"There must be consequences for the men who reportedly gang-raped a six-year-old child, who slit the throats of elderly villagers, who hanged women for resisting looting, and shot fleeing civilians in the swamps where they hid," he said.

At least 120 women and girls were raped or gang-raped, with one woman still bleeding from childbirth when she was assaulted, the report said. At least 132 other women and girls were also abducted.

There has not been any reaction to the report from the South Sudanese government.

The UN report said opposition forces had also carried out armed attacks that caused civilian casualties.

South Sudan rebels on Monday rejected a peace plan to reinstate their leader Riek Machar as vice president, under a deal reached at talks in Uganda.

They said it failed to dilute the strong power base of the country's president.

South Sudan is reeling from the effects of a four-and-a-half year civil war, which has killed tens of thousands, pushed millions to the brink of famine and created Africa's largest refugee crisis since the 1994 Rwandan genocide.

A "permanent" ceasefire was agreed upon by the two warring sides - led by President Salva Kiir and Riek Machar - last month, raising hopes of peace to end the country's devastating war that dates back to December 2013.

South Sudan's civil war broke out in December 2013 when Kiir accused his then-deputy Machar of plotting a coup, dashing the optimism that accompanied independence from Sudan just two years earlier.

Multiple attempts at peace deals have failed in the past leaving long-suffering citizens wondering whether this latest attempt at peace would fall apart as well.